Preheat grill, then squeeze the juice of the lime over the salmon fillet. Generously sprinkle salmon rub over salmon fillet, coating evenly.
Cut open avocado and remove flesh, crushing to an even texture. Add ranch dressing, garlic, and mix well.
Grill salmon over a medium high heat until done. Break or chop salmon into small pieces and distribute among warmed tortillas. Top with avocado dressing, diced tomatoes, and red onion.